A 67-year-old man is brought to the Emergency Department by his wife. She explains that he fell suddenly, could not get out of his bed, and complained of feeling sick. The examination revealed a left-sided weakness of the upper and lower extremities, a lack of most movement of the right eye, and a dilated pupil on the right. MRI shows an infarcted area in the brainstem. This man’s dilated pupil is due to damage to which of the following fiber populations?
- Preganglionic fibers from the Edinger-Westphal nucleus
- Preganglionic fibers from the inferior salivatory nucleus
- Postganglionic fibers from the ciliary ganglion
- Postganglionic fibers from the geniculate ganglion
- Postganglionic fibers from the superior cervical ganglion
The lesion in this man is central (brainstem) and involves the third nerve. Consequently, the damage is to the preganglionic parasympathetic fibers in the root of the oculomotor (III) nerve; this removes the parasympathetic influence (pupil constriction) that originates from the Edinger-Westphal nucleus
No comments:
Post a Comment